U.S. patent application number 14/840250 was filed with the patent office on 2016-03-10 for plasma processing device and plasma processing method.
The applicant listed for this patent is Tokyo Electron Limited. Invention is credited to Shigehiro MIURA, Jun SATO.
Application Number | 20160071722 14/840250 |
Document ID | / |
Family ID | 55438158 |
Filed Date | 2016-03-10 |
United States Patent
Application |
20160071722 |
Kind Code |
A1 |
MIURA; Shigehiro ; et
al. |
March 10, 2016 |
PLASMA PROCESSING DEVICE AND PLASMA PROCESSING METHOD
Abstract
A plasma processing apparatus includes a processing chamber. A
turntable to receive a substrate thereon is provided in the
processing chamber. A first plasma processing area is provided in a
predetermined location in a circumferential direction of the
turntable and configured to perform a first plasma process by
generating first plasma from a first plasma gas. A second plasma
processing area is provided apart from the first plasma processing
area in the circumferential direction of the turntable and
configured to perform a second plasma process by generating second
plasma from a second plasma gas. A separation area is provided in
each of two locations between the first plasma processing area and
the second plasma processing area and configured to prevent the
first plasma gas and the second plasma gas from mixing with each
other by separating the first plasma processing area from the
second plasma processing area.
Inventors: |
MIURA; Shigehiro; (Iwate,
JP) ; SATO; Jun; (Iwate, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited |
Tokyo |
|
JP |
|
|
Family ID: |
55438158 |
Appl. No.: |
14/840250 |
Filed: |
August 31, 2015 |
Current U.S.
Class: |
438/694 ;
118/719; 156/345.55; 438/710 |
Current CPC
Class: |
H01J 37/32752 20130101;
H01L 21/0234 20130101; H01J 37/32366 20130101; H01L 21/0228
20130101; H01L 21/68764 20130101; C23C 16/45536 20130101; C23C
16/45551 20130101; H01L 21/68771 20130101; H01L 21/02164 20130101;
H01J 37/32513 20130101; H01J 37/32899 20130101; C23C 16/4584
20130101; H01L 21/31116 20130101; H01J 37/32458 20130101; H01J
37/32715 20130101 |
International
Class: |
H01L 21/02 20060101
H01L021/02; H01L 21/311 20060101 H01L021/311; H01L 21/687 20060101
H01L021/687; H01J 37/32 20060101 H01J037/32; H01L 21/67 20060101
H01L021/67; C23C 16/455 20060101 C23C016/455; C23C 16/458 20060101
C23C016/458 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2014 |
JP |
2014-183609 |
Claims
1. A plasma processing apparatus comprising: a processing chamber;
a turntable to receive a substrate thereon provided in the
processing chamber; a first plasma processing area provided in a
predetermined location in a circumferential direction of the
turntable and configured to perform a first plasma process by
generating first plasma from a first plasma gas; a second plasma
processing area provided apart from the first plasma processing
area in the circumferential direction of the turntable and
configured to perform a second plasma process by generating second
plasma from a second plasma gas; and a separation area provided in
each of two locations between the first plasma processing area and
the second plasma processing area and configured to prevent the
first plasma gas and the second plasma gas from mixing with each
other by separating the first plasma processing area from the
second plasma processing area.
2. The plasma processing apparatus as claimed in claim 1, wherein
the first plasma processing area includes a first plasma gas nozzle
to supply the first plasma gas, wherein the second plasma
processing area includes a second plasma gas nozzle to supply the
second plasma gas, and wherein the separation area includes a
separation gas nozzle.
3. The plasma processing apparatus as claimed in claim 1, wherein
the first plasma processing area is an area configured to perform
an etching process, and the second plasma processing area is an
area configured to perform a modification process after the etching
process.
4. The plasma processing apparatus as claimed in claim 1, wherein
the first plasma processing area and the second plasma processing
area include side walls protruding from a ceiling surface of the
processing chamber toward the turntable provided to prevent the
first plasma gas and the second plasma gas from flowing out of the
first plasma processing area and the second plasma processing area,
respectively.
5. The plasma processing apparatus as claimed in claim 2, wherein
the separation area includes a convex portion protruding from a
ceiling surface of the processing chamber toward the turntable so
as to form a narrow space between a lower surface thereof and an
upper surface of the turntable, and a groove provided in the convex
portion and having a surface higher than the lower surface of the
convex portion to accommodate the separation gas nozzle therein,
and prevents the first plasma gas and the second plasma gas from
mixing with each other by supplying the separation gas from the
separation gas nozzle.
6. The plasma processing apparatus as claimed in claim 1, wherein a
fluoride-containing gas is supplied to the first plasma processing
area as the first plasma gas, wherein a hydrogen-containing gas is
supplied to the second plasma processing area as the second plasma
gas, and wherein a noble gas or nitrogen gas is supplied to the
separation area.
7. The plasma processing apparatus as claimed in claim 1, wherein
an area divided by the separation area in the circumferential
direction includes exhaust openings in a bottom surface of the
processing chamber.
8. The plasma processing apparatus as claimed in claim 7, wherein
the exhaust openings are provided downstream of the first plasma
processing area and the second plasma processing area in a
rotational direction of the turntable, respectively.
9. The plasma processing apparatus as claimed in claim 1, wherein
the turntable is rotatable in a direction that causes the substrate
received thereon to pass in the following order of the first plasma
processing area, a first separation area, the second plasma
processing area, and a second separation area.
10. A plasma processing method, comprising steps of: performing a
first plasma process on a substrate by generating first plasma from
a first plasma gas; purging the substrate subject to the first
plasma process by a first purge gas; performing a second plasma
process on the purged substrate by generating second plasma from a
second plasma gas; purging the substrate subject to the second
plasma process by a second purge gas; and performing two types of
plasma processes constituted of the first plasma process and the
second plasma process alternately by repeating a cycle constituted
of steps of performing the first plasma process, purging the
substrate subject to the first plasma process, performing the
second plasma process and purging the substrate subject to the
second plasma process a plurality of times in a constant
period.
11. The plasma processing method as claimed in claim 10, wherein
the first plasma process is an etching process, and wherein the
second plasma process is a modification process after the etching
process.
12. The plasma processing method as claimed in claim 11, wherein a
film is deposited on a surface of the substrate, wherein the
etching process is a process of etching the film deposited on the
substrate, and wherein the modification process is a process of
modifying the etched film.
13. The plasma processing method as claimed in claim 12, wherein
the etching process is a process of etching the film at a molecular
layer level, and wherein the modification process is a process of
modifying a surface of the etched film at a molecular layer
level.
14. The plasma processing method as claimed in claim 11, wherein
the first plasma gas is a fluoride-containing gas, wherein the
second plasma gas is a hydrogen-containing gas, and wherein the
purge gas is a noble gas or nitrogen gas.
15. The plasma processing method as claimed in claim 10, wherein a
period of time required for the cycle is longer than zero seconds
and equal to or shorter than 30 seconds.
16. The plasma processing method as claimed in claim 15, wherein
the period of time required for the cycle is equal to or longer
than 0.25 seconds and equal to or shorter than 12 seconds.
17. The plasma processing method as claimed in claim 10, further
comprising steps of: placing a plurality of substrates on a
turntable provided in a processing chamber along a circumferential
direction of the turntable, wherein the processing chamber includes
a first plasma processing area to perform the first plasma process,
a first purge area to purge the substrate subject to the first
plasma process by the purge gas, a second plasma processing area to
perform the second plasma process, and a second purge area to purge
the substrate subject to the second plasma process arranged along a
rotational direction of the turntable in this order, and the step
of performing two of the types of plasma processes is performed by
rotating the turntable at a predetermined rotational speed.
18. The plasma processing method as claimed in claim 17, wherein
the first plasma processing area is separated from the second
plasma processing area by the first and second purge areas, wherein
the step of purging the substrate subject to the first plasma
process by the purge gas prevents the second plasma gas from mixing
into the first plasma processing area during the step of performing
the first plasma process, and wherein the step of purging the
substrate subject to the second plasma process by the purge gas
prevents the first plasma gas mixing into the second plasma
processing area during the step of performing the second plasma
process.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is based upon and claims the benefit
of priority of Japanese Patent Application No. 2014-183609, filed
on Sep. 9, 2014, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a plasma processing
apparatus and a plasma processing method.
[0004] 2. Description of the Related Art
[0005] Conventionally, as disclosed in Japanese Patent Application
Publication No. 2010-56470, a variety of films constituting
semiconductor devices is demanded to be thinner and more uniform
with miniaturization of circuit patterns in the semiconductor
devices. What is called MLD (Molecular Layer Deposition) or ALD
(Atomic Layer Deposition) is known as a film deposition method for
responding to the demand. In the method, a first reaction gas is
absorbed on a surface of a substrate by supplying the first
reaction gas to the substrate, and then the first gas adsorbed on
the surface of the substrate is caused to react with a second
reaction gas by supplying the second reaction gas to the substrate,
thereby depositing a film composed of a reaction product of the
first reaction gas and the second reaction gas on the substrate.
According to such a method of depositing a firm, because the
reaction gas can adsorb on the surface of the substrate in a
(quasi-)self-saturation manner, high film thickness
controllability, excellent uniformity, and excellent filling
characteristics can be achieved.
[0006] However, with the miniaturization of circuit patterns, for
example, filling a trench and a space is sometimes difficult even
in the molecular layer deposition method with the increasing aspect
ratio of the trench in a trench device separation structure or of a
space in a line-and-space pattern. For example, when trying to fill
the space having a width of about 30 nm with a silicon oxide film,
because the reaction gas is difficult to go to a bottom part of a
narrow space, the film becomes thick in the vicinity of the upper
end of a side wall of the line that partitions the space and
becomes thin on the bottom part side. This sometimes causes a void
to be generated in the silicon oxide film filling the space. For
example, when such a silicon oxide film is etched in a subsequent
etching process, an opening in communication with the void is
sometimes formed in an upper surface of the silicon oxide film. On
this occasion, contamination is liable to occur by allowing an
etching gas (or an etching solution) to go into the void from the
opening, or a defect is liable to occur by allowing metal to go
into the void in a subsequent metallization process.
[0007] Such a problem can occur in CVD (Chemical vapor Deposition)
without being limited to ALD. For example, when forming a
conductive contact hole (so-called a plug) by filling a contact
hole formed in a semiconductor substrate with a conductive
material, a void may be generated in the plug. As disclosed in
Japanese Patent Application Publication No. 2003-142484, to prevent
this, a method is proposed of forming a conductive contact hole in
which a void is reduced by repeating a step of removing overhangs
projecting toward the center of the contact hole of the conductive
material formed in the upper part or on the top of the contact hole
when filling the contact hole with the conductive material by an
etch back process.
[0008] However, in the etching process used in filling the
above-mentioned space and contact hole with the conductive
material, an improvement in film quality after the etching process
is not always enough, and there has been a concern about a residue
of a fluoride component of a fluoride-containing gas used in the
etching process, which has been liable to decrease the film
quality.
SUMMARY OF THE INVENTION
[0009] In view of the above, embodiments of the present invention
aims to provide a plasma processing apparatus and a plasma
processing method that can reduce a fluoride concentration in a
film.
[0010] In an embodiment of the present invention, there is provided
a plasma processing apparatus that includes a processing chamber. A
turntable to receive a substrate thereon is provided in the
processing chamber.
[0011] A first plasma processing area is provided in a
predetermined location in a circumferential direction of the
turntable and configured to perform a first plasma process by
generating first plasma from a first plasma gas. A second plasma
processing area is provided apart from the first plasma processing
area in the circumferential direction of the turntable and
configured to perform a second plasma process by generating second
plasma from a second plasma gas. A separation area is provided in
each of two locations between the first plasma processing area and
the second plasma processing area and configured to prevent the
first plasma gas and the second plasma gas from mixing with each
other by separating the first plasma processing area from the
second plasma processing area.
[0012] In another embodiment of the present invention, there is
provided a plasma processing method. In the method, a first plasma
process is performed on a substrate by generating first plasma from
a first plasma gas. The substrate subject to the first plasma
process is purged by a purge gas. A second plasma process is
performed on the purged substrate by generating second plasma from
a second plasma gas. The substrate subject to the second plasma
process is purged by a purge gas. Two types of plasma processes
constituted of the first plasma process and the second plasma
process alternately are performed by repeating a cycle constituted
of steps of performing the first plasma, purging the substrate
subject to the first plasma process, performing the second plasma
process and purging the substrate subject to the second plasma
process a plurality of times in a constant period.
[0013] Additional objects and advantages of the embodiments are set
forth in part in the description which follows, and in part will
become obvious from the description, or may be learned by practice
of the invention. The objects and advantages of the invention will
be realized and attained by means of the elements and combinations
particularly pointed out in the appended claims. It is to be
understood that both the foregoing general description and the
following detailed description are exemplary and explanatory and
are not restrictive of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a vertical cross-sectional view illustrating an
example of a plasma processing apparatus according to an embodiment
of the present invention;
[0015] FIG. 2 is a horizontal cross-sectional view illustrating an
example of the plasma processing apparatus according to an
embodiment of the present invention;
[0016] FIG. 3 is a horizontal cross-sectional view illustrating an
example of the plasma processing apparatus according to an
embodiment of the present invention;
[0017] FIG. 4 is an exploded perspective view illustrating a part
of the inside of the plasma processing apparatus according to an
embodiment of the present invention is applied;
[0018] FIG. 5 is a vertical cross-sectional view illustrating a
part of the inside of the plasma processing apparatus according to
an embodiment of the present invention;
[0019] FIG. 6 is a perspective view illustrating a part of the
inside of the plasma processing apparatus according to an
embodiment of the present invention;
[0020] FIG. 7 is a vertical cross-sectional view illustrating a
part of the inside of the plasma processing apparatus according to
an embodiment of the present invention;
[0021] FIG. 8 is a plan view illustrating a part of the inside of
the plasma processing apparatus according to an embodiment of the
present invention;
[0022] FIG. 9 is a perspective view illustrating a Faraday shield
of the plasma processing apparatus according to an embodiment of
the present invention;
[0023] FIG. 10 is a perspective view illustrating a part of the
Faraday shield of the plasma processing apparatus according to an
embodiment of the present invention;
[0024] FIGS. 11A through 11D are process drawings illustrating an
example of a plasma processing method according to an embodiment of
the present invention;
[0025] FIGS. 12A and 12B are a series of process drawings for
explaining a modification process of the plasma processing method
according to an embodiment of the present invention;
[0026] FIG. 13 is a graph showing a result of analysis of a
fluoride concentration in a SiO.sub.2 film after performing a
conventional modification process;
[0027] FIGS. 14A and 14B are diagrams showing simulation results
indicating a separation state of hydrogen gas in the plasma
processing apparatus according to an embodiment of the present
invention;
[0028] FIGS. 15A and 15B are diagrams showing simulation results
indicating a separation state of NF.sub.3 gas in the plasma
processing apparatus according to an embodiment of the present
invention;
[0029] FIGS. 16A and 16B are diagrams showing simulation results
indicating separation characteristics of a separation gas in terms
of pressure of the plasma processing apparatus according to an
embodiment of the present invention; and
[0030] FIGS. 17A and 17B are diagrams showing simulation results
indicating separation characteristics of a separation gas in terms
of mass concentration of the plasma processing apparatus according
to an embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] A description is given below of embodiments of the present
invention with reference to the accompanying drawings.
[0032] To begin with, a description is given below of an example of
an etching apparatus to which a plasma processing apparatus and a
plasma processing method according to an embodiment of the present
invention are applied. The plasma processing apparatus and the
plasma processing method according to an embodiment of the present
invention are applicable not only to an etching apparatus, but also
to all kinds of apparatuses that perform a plasma process such as a
film deposition apparatus and a substrate processing apparatus that
performs both of the etching and the film deposition. However, in
the embodiment, a description is given below of an example in which
a plasma processing apparatus according to an embodiment of the
present invention is configured as an etching apparatus.
[0033] A description is given of an example of an etching apparatus
to which a plasma processing apparatus of the embodiment of the
present invention is applied, with reference to FIGS. 1 through 10.
As illustrated in FIGS. 1 and 2, the etching apparatus of the
embodiment includes a processing chamber 1 having a substantially
circular planar shape, and a turntable 2 provided inside the
processing chamber 1, which has a rotational center positioned at
the center of the processing chamber 1. Furthermore, as described
in detail below, the etching apparatus is configured to etch a thin
film deposited on a surface of a wafer W by ALE (Atomic Layer
Etching) and to perform a plasma modification on the thin film
after the etching. At this time, to perform the plasma
modification, the etching apparatus is configured so that the thin
film does not contain a fluoride component or contains the fluoride
component as little as possible by removing the fluoride component
contained in the thin film by plasma. More specifically, the
etching is often performed by using a fluoride-containing etching
gas in a semiconductor process, and when the fluoride component
remains in a film that is an etching object, a device property
becomes worse. In particular, when the fluoride component remains
in a silicon-based film such as SiO.sub.2, SiN and the like, the
remaining fluoride component adversely affects the device property.
In the meantime, as discussed above, because the
fluoride-containing gas such as NF.sub.3 or the like is often used
as the etching gas, when etching a film, a fluoride concentration
in the film generally increases, and decreasing the fluoride
concentration as little as possible is a technical problem. Hence,
the etching apparatus of the embodiment performs a periodical small
quantity of etching and effectively removes the fluoride component
remaining in the film by a periodical modification process, but
details of this point will be described later. Subsequently, a
detailed description is given below of each part of the etching
apparatus.
[0034] The processing chamber 1 includes a ceiling plate 11 and a
chamber body 12, and the ceiling plate 11 is detachable from the
chamber body 12. At the center part on the top surface side of the
ceiling plate 11, a separation gas supply tube 51 is connected
thereto for supplying Ar gas as a separation gas, for preventing
different types of processing gases from mixing with each other, at
a central area C in the processing chamber 1. Furthermore, FIG. 1
illustrates a seal member 13 (for example, an O-ring) provided in a
ring shape along the outer peripheral part of the top surface of
the chamber body 12.
[0035] The center part of the turntable 2 is fixed to a core part
21 having a substantially cylindrical shape. The turntable 2 is
rotatable around a vertical axis (in a clockwise direction in this
example), by a rotary shaft 22, which is connected to the bottom
surface of the core part 21 and which extends in the vertical
direction. A driving unit 23 is a driver that rotates the rotary
shaft 22 around the vertical axis. A case body 20 accommodates the
rotary shaft 22 and the driving unit 23. A flange part of the top
surface of this case body 20 is attached to the bottom side of a
bottom part 14 of the processing chamber 1 in a gastight manner.
Furthermore, a purge gas supply tube 72 is connected to an area
below the turntable 2 of the case body 20, for supplying Ar gas as
a purge gas. In the processing chamber 1, at the part of the bottom
part 14 at the outer peripheral side of the core part 21, a ring
shape is formed adjacent to the turntable 2 from below the
turntable 2, and the ring shape constitutes a protruding part
12a.
[0036] As illustrated in FIGS. 2 and 3, on the surface of the
turntable 2, circular recessed portions 24 are provided as
substrate receiving areas for receiving wafers W thereon which are
a plurality of (for example, five) substrates, along the rotational
direction (circumferential direction). The diameter and the depth
of the recessed portions 24 are set such that when wafers W having
a diameter of, for example, 300 mm, are placed on the recessed
portions 24, the surface of the wafer W and the surface of the
turntable 2 (areas where the wafers W are not placed) are flat. At
the bottom of the recessed portions 24, through holes (not
illustrated in the drawings) are formed to allow a plurality of
(e.g., three) lift pins to penetrate therethrough in order to raise
the wafer W from below and to move the wafer W up and down.
[0037] As illustrated in FIGS. 2 and 3, four nozzles 31, 32, 41 and
42 made of, for example, quartz, are radially arranged at positions
above the turntable 2 facing the recessed portions 24. The nozzles
31, 32, 41 and 42 are arranged interposing gaps in the
circumferential direction (a rotational direction of the turntable
2) of the processing chamber 1. For example, each of the nozzles
31, 32, 41 and 42 is attached so as to extend horizontally facing
the wafer W from the outer peripheral wall of the processing
chamber 1 toward the central area C. In this example, a first
plasma gas nozzle 31, a separation gas nozzle 41, a second plasma
gas nozzle 32, and a separation gas nozzle 42 are arranged in this
order in a clockwise fashion (rotational direction of turntable 2)
as viewed from a transfer opening 15 described below. As
illustrated in FIG. 1, above the first plasma gas nozzle 31, a
first plasma generation unit 80 is provided to convert a gas
discharged from the first plasma gas nozzle 31 into plasma.
Moreover, above the second plasma gas nozzle 32, a second plasma
generation unit 130 is provided to convert a gas discharged from
the second plasma gas nozzle 32 into plasma. In FIG. 1, the second
plasma generation unit 130 is not depicted.
[0038] Details of the first and second plasma generation units 80
and 130 are described later.
[0039] The plasma gas nozzles 31 and 32 constitute a first plasma
gas supply unit and a second plasma gas supply unit, respectively.
The separation gas nozzles 41 and 42 constitute separation gas
supply units, respectively. Note that FIG. 2 illustrates a state in
which the plasma generation unit 80 and a case 90 that will be
described later have been removed such that the plasma gas nozzles
31 and 32 can be seen, and FIG. 3 illustrates a state in which the
plasma generation units 80 and 130 and cases 90 and 140 are
attached. Furthermore, in FIG. 1, the plasma generation unit 80 is
schematically illustrated by a dashed-dotted line (the plasma
generation unit 130 is not illustrated in FIG. 1).
[0040] Each of the nozzles 31, 32, 41 and 42 is connected to a gas
supply source (not illustrated in the drawings) described below,
through a flow rate adjustment valve. That is to say, the first
plasma gas nozzle 31 is connected to a supply source of an etching
gas, and for example, a fluoride-containing gas such as NH.sub.3
gas or the like is used as the etching gas. The second plasma gas
nozzle 32 is connected to a supply source of a modification gas,
and for example, hydrogen gas and the like are used as the
modification gas because hydrogen gas can react with fluoride and
remove fluoride from a film by becoming HF and escaping from the
film together with fluoride. The first plasma gas nozzle 31 is
connected to a supply source of mixed gas of, for example, Ar
(argon) gas and NF.sub.3 gas. Each of the separation gas nozzles 41
and 42 is connected to a gas supply source of an inactive gas
(including a noble gas) such as Ar gas, N.sub.2 gas or the like
that is the separation gas. As a matter of convenience, a
description is given below of an example in which the film to be
etched is a SiN film; the etching gas supplied from the first
plasma gas nozzle 31 is a mixed gas of Ar and NF.sub.3; the
modification gas supplied from the second plasma gas nozzle 32 is a
mixed gas of Ar and H.sub.2; and the separation gas is Ar gas.
Although N.sub.2 gas may be used as the separation gas when the
film to be etched is a SiN film, Ar gas is preferred to be used as
the separation gas when the film to be etched is the SiO.sub.2 film
so as not to produce SiON and the like. Hereinafter, the etching
gas supplied from the first plasma gas nozzle 31 may be referred to
as a first plasma gas, and the modification gas supplied from the
second plasma gas nozzle 32 may be referred to as a second plasma
gas.
[0041] As illustrated in FIG. 7, gas discharge holes 33 and 43 are
formed in lower surfaces of the plasma gas nozzles 31 and 32, and
the separation gas nozzles 41 and 42, respectively, at a plurality
of positions along the radial direction of the turntable 2, for
example, at regular intervals. More specifically, the gas discharge
holes 33 having a diameter of, for example, 0.3 mm through 0.5 mm,
are formed in a lower lateral surface of the plasma gas nozzle 31,
at a plurality of positions along the longitudinal direction of the
plasma gas nozzle 33, for example, at regular intervals, so as to
face the upstream side in the rotation direction (on the side of
the second processing gas nozzle 32) and the bottom side (obliquely
downward) of the turntable 2. The reason of setting the direction
of the gas discharge holes 33 of the plasma gas nozzle 31 as
described above is described below. These nozzles 31, 32, 41 and 42
are arranged such that the distance between the bottom edge of the
nozzles 31, 32, 41 and 42 and the top surface of the turntable 2
is, for example, approximately 1 mm through 5 mm.
[0042] Areas below the first and second plasma gas nozzles 31 and
32 are referred to as a first plasma processing area P1 where the
SiO.sub.2 film deposited on the wafer W is to be etched, and a
second plasma processing area P2 where the surface of the etched
SiO.sub.2 film is to be modified, respectively. The separation gas
nozzles 41 and 42 are for forming separation areas D that separate
the first plasma processing area P1 from the second plasma
processing area P2. As illustrated in FIGS. 2 and 3, convex
portions 4 having a substantially sector shape, are provided on the
ceiling plate 11 of the processing chamber 1 in the separation
areas D, and the separation gas nozzles 41 and 42 are accommodated
in grooves 46 that are formed in the convex portions 4. Therefore,
on both sides of each of the separation gas nozzles 41 and 42 in
the circumferential direction of the turntable 2, there are
provided low ceiling surfaces 44 (first ceiling surfaces) that
correspond to the bottom surfaces of the convex portions 4, in
order to prevent the different types of processing gases from being
mixed with each other. On both sides of the ceiling surfaces 44 in
the circumferential direction, there are provided ceiling surfaces
45 (second ceiling surfaces) that are lower than the ceiling
surfaces 44. The outer peripheral parts (the outer edge side of the
processing chamber 1) of the convex portions 4 form bent portions
which are bent into an L shape so as to face the outer edge surface
of the turntable 2 and to be slightly spaced apart from the chamber
body 12, in order to prevent the different types of processing
gases from being mixed with each other.
[0043] As illustrated in FIGS. 2 and 3, the separation areas D are
provided in two distant spaces between the first plasma processing
area P1 in which the etching process is performed and the second
plasma processing area P2 in which the modification process is
performed. Hence, the first plasma processing area P1 is reliably
separated from the second plasma processing area P2 by way of the
separation areas D. For example, when (Ar+NF.sub.3) gas is supplied
from the first plasma gas nozzle 31 provided in the first plasma
processing area P1 and (Ar+H.sub.2) gas is supplied from the second
plasma processing gas nozzle 32 provided in the second plasma
processing area P2, and if NF.sub.3 gas and H.sub.2 gas mix with
each other in a predetermined concentration range (1.5 to 90.6%),
an explosion is liable to occur. Accordingly, to reliably prevent
the mixture of NF.sub.3 gas and H.sub.2 gas, the separation areas D
are provided in two of the distant spaces between the first plasma
processing area P1 and the second plasma processing area P2,
respectively, thereby reliably preventing NF.sub.3 gas supplied
into the first plasma processing area P1 and H.sub.2 gas supplied
into the second plasma processing area P2 from mixing with each
other.
[0044] More specifically, NF.sub.3 gas and H.sub.2 gas react with
each other by the following chemical formula (1).
3H.sub.2+2NF.sub.3.fwdarw.6HF+N.sub.2 (1)
[0045] Here, when H.sub.2 gas and NF.sub.3 gas are in a
predetermined concentration range, the explosion is liable to occur
as described above, but even if the explosion does not occur, HF is
produced as a result of the reaction. Because HF is a corrosive
gas, when HF gas is generated and attaches to the inner wall and
the like of the processing chamber 1, HF gas is liable to corrode
the attached portion such as the inner wall. Hence, even if the
explosion does not occur, the plasma processing apparatus is
preferred to have a structure that prevents NF.sub.3 gas and
H.sub.2 gas from mixing with each other. On this point, because the
plasma processing apparatus of the embodiment includes the
separation areas D that separate the first plasma processing area
P1 from the second plasma processing area P2 by the convex portions
4 and the supply of the separation gas (Ar gas), the explosion and
the internal corrosion of the processing chamber 1 can be reliably
prevented.
[0046] The separation areas D may be referred to as purge areas D,
and the separation gas may be referred to as a purge gas because
the separation gas plays a role equivalent to the purge gas.
[0047] In addition, although the first and second plasma processing
areas P1 and P2 have a structure that prevents a gas from going
into the first and second plasma processing areas P1 and P2 from
the outside, respectively, a description is given later on this
point.
[0048] The first and second plasma gas nozzles 31 and 32 are both
provided at positions on the upstream side of the first and second
plasma processing area, respectively. This is intended to promptly
convert NF.sub.3 gas and H.sub.2 gas supplied from the first and
second plasma gas nozzles 31 and 32, respectively, into plasma and
to reliably perform the plasma process while the wafer W passes the
first and second plasma processing areas P1 and P2.
[0049] Next, a detailed description is given of the plasma
generation unit 80. The plasma generation unit 80 is configured by
winding around an electrode 83 (or may be referred to as an
"antenna") to form a coil, which is constituted by a metal wire
such as copper (Cu) or the like. The plasma generation unit 80 is
provided on the ceiling plate 11 of the processing chamber 1 so as
to be partitioned from the inside area of the processing chamber 1
in a gastight manner. In this example, the electrode 83 is made of
a material formed by applying a nickel coating and gold coating on
a copper surface in this order. More specifically, as illustrated
in FIG. 4, an opening 11a that is open in a substantially sector
shape in a planar view is formed in the ceiling plate 11 above the
plasma gas nozzle 31 (specifically, from a position that is
slightly on the upstream side in the rotational direction of the
turntable 2 with respect to the plasma gas nozzle 31, to a position
that is slightly closer to the plasma gas nozzle 31 than the
separation area D on the downstream side in the rotational
direction of the plasma gas nozzle 31).
[0050] The opening 11a is formed from a position that is spaced
apart from the rotational center of the turntable 2 toward the
outer peripheral side by, for example, approximately 60 mm, to a
position that is spaced apart from the outer edge of the turntable
2 toward the outside by, for example, approximately 80 mm.
Furthermore, the edge of the opening 11a on the center side of the
turntable 2 in a planar view is hollowed into an arc shape along
the outer edge of a labyrinth structure part 110, so as not to
interfere with (to avoid) the labyrinth structure part 110
(described below) provided at the central area C of the processing
chamber 1. Furthermore, as illustrated in FIGS. 4 and 5, in the
opening 11a, for example, three stage parts 11b are formed in the
circumferential direction, such that the diameter of the opening
11a is gradually reduced from the top side of the ceiling plate 11
toward the bottom side of the ceiling plate 11. On the top surface
of the lowest one of the stage parts 11b (rim part), there is
formed a groove 11c in the circumferential direction as illustrated
in FIG. 5. A seal member, for example, an O-ring lid is arranged in
the groove 11c. Note that the groove 11c and the O-ring 11d are not
illustrated in FIG. 4.
[0051] In the opening 11a, as illustrated in FIG. 6, the case 90 is
arranged. In the case 90, the outer peripheral part on the top side
extends out horizontally along the circumferential direction in a
flange shape forming a flange part 90a. Furthermore, the center
part of the case 90 is formed so as to be hollowed toward the
inside area of the processing chamber 1 below the case 90. This
case 90 is constituted by a magnetically permeable body (a material
through which magnetic force is permeated), made of a dielectric
material such as quartz, in which the thickness t of the hollowed
part is, for example, 20 mm as illustrated in FIG. 9. Furthermore,
when the wafer W is positioned at the bottom of the case 90, on the
central area C side, the distance between the inner wall surface of
the case 90 and the edge of the wafer W is 70 mm, and on outer
peripheral side of the turntable 2, the distance between the inner
wall surface of the case 90 and the outer edge of the wafer W is 70
mm. Thus, the angle .alpha. formed by the two sides of the opening
11a at the upstream side and the downstream side in the rotational
direction of the turntable 2 and the rotational center of the
turntable 2 is, for example, 68.degree..
[0052] The case 90 is made of a material having a high anti-plasma
etching property such as high purity quartz, high purity alumina,
and yttria. Otherwise, at least the surface layer part of the case
90 is coated by this material. Thus, the case 90 is basically made
of a dielectric material.
[0053] When the case 90 is fitted in the opening 11a, the flange
part 90a is engaged with the bottommost stage part 11b. Then, the
stage parts 11b (ceiling plate 11) and the case 90 are connected in
a gastight manner by the O-ring 11d. Furthermore, while the flange
part 90a is pressed downward along the circumferential direction by
a suppressing member 91, which is formed to have a frame-like shape
extending along the outer edge of the opening 11a, the suppressing
member 91 is fixed to the ceiling plate 11 by a bolt (not
illustrated in the drawings), thereby setting the internal
atmosphere of the processing chamber 1 in a gastight state. When
the case 90 is fixed to the ceiling plate 11 in a gastight manner
as described above, the distance h between the bottom surface of
the case 90 and the surface of the wafer W on the turntable 2 is
set at 4 mm through 60 mm (30 mm in this example). Note that FIG. 6
is a view from the bottom of the case 90.
[0054] As illustrated in FIGS. 1 and 5 through 7, in order to
prevent N.sub.2 gas and O.sub.3 gas from entering an area under the
case 90, a projection part 92 for regulating a gas is formed on the
bottom surface of the case 90. More specifically, the outer edge of
the case 90 vertically extends out downward (toward the turntable
2) along the circumferential direction, thereby forming the
projection part 92. The plasma gas nozzle 31 is accommodated, on
the upstream side in the rotational direction of the turntable 2,
in the area that is surrounded by the inner peripheral surface of
the projection part 92, the bottom surface of the case 90, and the
top surface of the turntable 2.
[0055] Here, the projection part 92 is formed on the lower surface
side of the case 90 so as to prevent a gas from going into the area
under the case 90 (plasma space 10) from the outside. As discussed
above, because the first plasma processing area 21 is separated
from the second plasma processing area P2 by the separation areas D
that separate the first plasma processing area P1 from the second
plasma processing area P2 by supplying Ar gas, a space between the
separation area D and the first plasma processing area P1 is filled
with Ar gas, but when Ar gas from the outside enters the first
plasma processing area P1, the concentration of NF.sub.3 gas
decreases. Therefore, to prevent Ar gas from entering the area
under the case 90, the projection part 92 is formed in the lower
surface of the case 90.
[0056] In addition, when the film to be etched is a SiN film,
N.sub.2 gas is sometimes used as the separation gas. In this case,
because the gas supplied from the plasma gas nozzle 31 is converted
into plasma in the area under the case 90 (plasma space 10), when
N.sub.2 gas enters the plasma space 10, plasma of N.sub.2 gas and
plasma of O.sub.3 gas (O.sub.2 gas) react with each other and NOx
gas is generated. When NOx gas is generated, the members in the
processing chamber 1 are corroded. Therefore, in order to reduce
N.sub.2 gas entering the area under the case 90, the projection
part 92 is formed in the lower surface of the case 90.
[0057] The projection part 92 on the base end side of the plasma
gas nozzle 31 (on the lateral wall side of the processing chamber
1) is cut out into a substantially arc shape along the external
shape of the plasma gas nozzle 31. The distance d (see FIG. 7)
between the bottom surface of the projection part 92 and the top
surface of the turntable 2 is 0.5 mm through 4 mm (2 mm in this
example). The width and the height of the projection part 92 are
set at, for example, 10 mm and 28 mm, respectively. Note that FIG.
7 is a cross-sectional view of the processing chamber 1 cut along
the rotational direction of the turntable 2.
[0058] Furthermore, during the etching process, the turntable 2
rotates in a clockwise fashion, and therefore, along with the
rotation of the turntable 2, N.sub.2 gas tends to enter the bottom
side of the case 90 through a gap between the turntable 2 and the
projection part 92. Therefore, in order to prevent N.sub.2 gas from
entering the bottom side of the case 90 through this gap, a gas is
discharged from the bottom side of the case 90 to the gap. More
specifically, as illustrated in FIGS. 5 and 7, the gas discharge
holes 33 of the plasma gas nozzle 31 are arranged so as to face
toward the gap, i.e., the gas discharge holes 33 are arranged on
the upstream side in the rotational direction of the turntable 2
and are arranged to face downward. For example, the angle .theta.
of the direction of the gas discharge holes 33 of the plasma gas
nozzle 31 with respect to the vertical axis is approximately set at
45.degree. as illustrated in FIG. 7.
[0059] Here, referring to the O-ring 11d sealing the area between
the ceiling plate 11 and the case 90 from below the case 90 (plasma
space 10), as illustrated in FIG. 5, the projection part 92 is
formed in the circumferential direction between the plasma space 10
and the O-ring 11d. Hence, to prevent the O-ring 11d from being
directly exposed to plasma, the O-ring 11d is isolated from the
plasma space 10. Accordingly, for example, even if the plasma in
the plasma space 10 is likely to diffuse toward the O-ring 11d,
because the plasma passes through the part below the projection
part 92, the plasma is likely to become inactivated before reaching
the O-ring 11d.
[0060] A grounded Faraday shield 95, which is formed to
substantially extend along the inner shape of the case 90, is
accommodated inside the case 90 (in the area that is caved in
downwards in the case 90). The grounded Faraday shield 95 is formed
of a metal plate that is made of a conductive plate-like body
having a thickness k of, for example, approximately 1 mm. In this
example, the Faraday shield 95 is made of a plate material that is
a copper (Cu) plate or a plate material formed by coating a copper
plate with a nickel (Ni) film or a gold (Au) film from below. That
is to say, the Faraday shield 95 includes a horizontal surface 95a
that is formed horizontally along the bottom surface of the case
90, and a vertical surface 95b extending upward along the
circumferential direction from the outer peripheral edge of the
horizontal surface 95a, and is formed to have a substantially
sector-like shape along the inner edge of the case 90 as viewed
from above. The Faraday shield 95 is formed by, for example,
performing a rolling process on a metal plate, or by bending upward
the area of the metal plate corresponding to an area outside the
horizontal surface 95a.
[0061] Furthermore, the upper edges of the Faraday shield 95 on the
right side and the left side as viewed from the rotational center
of the turntable 2, respectively horizontally extend toward the
right side and the left side, thereby forming support parts 96.
Furthermore, when the Faraday shield 95 is accommodated inside the
case 90, the bottom surface of the Faraday shield 95 and the top
surface of the case 90 contact each other, and the support parts 96
are supported by the flange part 90a of the case 90. On top of the
horizontal surface 95a, in order to insulate the Faraday shield 95
from the plasma generation unit 80 placed on the Faraday shield 95,
an insulating plate 94 is laminated, which has a thickness of, for
example, approximately 2 mm, and which is made of, for example,
quartz. A plurality of slits 97 is formed in the horizontal surface
95a. The shape and the arrangement layout of the slits 97 are
described below together with the description of the electrode 83
of the plasma generation unit 80. Note that the insulating plate 94
is not illustrated in FIGS. 8 and 9 described below.
[0062] The plasma generation unit 80 is configured to be
accommodated inside the Faraday shield 95. Thus, as illustrated in
FIGS. 4 and 5, the plasma generation unit 80 is arranged so as to
face the inside of the processing chamber 1 (wafer W on the
turntable 2), via the case 90, the Faraday shield 95, and the
insulating plate 94. The plasma generation unit 80 is configured by
winding the electrode 83 around the vertical axis, and the plasma
generation unit 80 includes two plasma generation parts 81 and 82
in this example. Each of the plasma generation parts 81 and 82 is
formed by winding around the electrode 83 in a triple helix. One of
the plasma generation parts 81 and 82 is referred to as first
plasma generation part 81 and the other one is referred to as a
second plasma generation part 82. As illustrated in FIGS. 4 and 5,
the first plasma generation part 81 has a substantially sector-like
shape extending along the inner edge of the case 90 in a planar
view. Furthermore, the first plasma generation unit 81 is arranged
such that the central area C and the outer peripheral edge are in
close contact with the inner walls of the case 90, so that it is
possible to radiate (supply) plasma along the part between the edge
of the wafer W on the central area C side and the outer edge part
of the turntable 2, when the wafer W is positioned under the first
plasma generation part 81. Note that a flow path through which
cooling water flows is formed inside the electrode 83, although not
illustrated.
[0063] As described above, by adopting a configuration in which the
electrode 83 of the plasma generation unit 80 is arranged outside
the processing chamber 1, and electric fields and magnetic fields
are introduced into the processing chamber 1 from the outside, the
electrode 83 does not have to be arranged inside the processing
chamber 1. Accordingly, it is possible to prevent metal
contamination inside the processing chamber 1, so that a
high-quality film can be deposited. However, because the case 90 is
a dielectric material made of high-purity quartz, compared to a
configuration in which the electrode 83 is inside the processing
chamber 1, there are cases where it is difficult to cause plasma
discharge. According to the plasma processing apparatus of an
embodiment of the present invention, a plasma processing apparatus
and a plasma processing method are provided that can stably cause
plasma discharge while adopting a configuration in which the
electrode 83 is provided outside the processing chamber 1.
[0064] The second plasma generation part 82 is provided between a
position that is about 200 mm away from the central position of the
wafer on the turntable 2 toward the periphery and a position that
is about 90 mm away from the outer edge of the turntable 2 toward
the periphery to be able to supply plasma to the wafer at the
peripheral side in the radial direction of the turntable 2. In
other words, when the turntable 2 rotates, the rotational speed is
higher on the peripheral side than on the central side. Due to
this, a quantity of plasma supplied to the wafer W is sometimes
smaller on the outer peripheral side than on the inner peripheral
side. Therefore, to supply the same quantity of plasma to the wafer
W along the radial direction of the turntable 2, in other words, to
compensate for the quantity of plasma supplied to the wafer W from
the first plasma generation unit 80, the second plasma generation
part 82 is provided.
[0065] The electrodes 83 included in the first plasma generation
part 81 and the second plasma generation part 82, are separately
connected to a high frequency power source 85 via a matching box
84. The high frequency power source 85 has a frequency of, for
example, 13.56 MHz, and output power of, for example, 5000 W.
Accordingly, the high frequency power can be separately adjusted
for the first plasma generation part 81 and the second plasma
generation part 82. Note that in FIG. 3, the matching boxes 84 and
the high frequency power sources 85 are illustrated in a simplified
manner. Furthermore, in FIGS. 1, 3, and 4, a connection electrode
86 is illustrated, for electrically connecting each of the first
and second plasma generation parts 81 and 82 to the matching box 84
and the high frequency power source 85.
[0066] Here, the high frequency power source 85 is able to change
the output (hereinafter, also simply referred to as "high frequency
output") of high frequency power supplied to the electrode 83. The
output of the high frequency power source 85 is set at, for
example, 3300 W, for a plasma process for regular film deposition
in a processing room of 600.degree. C. and at 1.8 Torr.
[0067] Next, a detailed description is given of the slits 97 of the
Faraday shield 95. Among the electric field and magnetic field
(electromagnetic field) generated in the first plasma generation
part 81 and the second plasma generation part 82, the slits 97
prevent the electric field components from going toward the wafer W
positioned below, and also causes the magnetic field to reach the
wafer W. That is to say, if the electric field reaches the wafer,
the electric wiring formed inside the wafer W may be electrically
damaged. In the meanwhile, because the Faraday shield 95 is made of
a grounded metal plate, unless slits 97 are formed, the electric
field will be blocked as well as the magnetic field. Furthermore,
if a large opening is formed at the bottom of the electrode 83, the
magnetic field will pass therethrough as well as the electric
field. Therefore, in order to block the electric field but let the
magnetic field through, the slits 97 are formed having the
following size and arrangement layout.
[0068] Specifically, as illustrated in FIG. 8, the slits 97 are
formed at the bottom position of the electrode 83 across the
circumferential direction, extending in a direction orthogonal to
the winding direction of each of the electrodes 83 of the first
plasma generation part 81 and the second plasma generation part 82.
Accordingly, for example, in the area where the electrode 83 is
arranged along the radial direction of the turntable 2, the slits
97 are formed in a linear shape or in an arc shape along the
tangential direction or the circumferential direction of the
turntable 2. Furthermore, in the area where the electrode 83 is
placed in an arc shape along the outer edge of the turntable 2, the
slits 97 are formed in a linear shape directed from the rotational
center toward the outer edge of the turntable 2. Furthermore, at
the part where the electrode 83 bends between the two areas, the
slits 97 are formed in a tilted direction with respect to the
circumferential direction and the radial direction of the turntable
2, so as to be orthogonal with respect to the direction in which
the electrode 83 extends at the bending part. Accordingly, multiple
slits 97 are arranged along the direction in which the electrode 83
extends.
[0069] Here, the high frequency power source 85 having a frequency
of 13.56 MHz is connected to the electrode 83 as described above.
The wavelength that corresponds to this frequency is 22 meters.
Therefore, the slits 97 are formed to have a width that is
approximately less than or equal to 1/10000 of this wavelength,
i.e., as illustrated in FIG. 9, to have a width d1 of 1 mm through
5 mm (2 mm in this example), and have a space d2 between the slits
97 of 1 mm through 5 mm (2 mm in this example). Furthermore as
illustrated in FIG. 8, the multiple slits 97 are formed in an area
ranging from a position that is approximately 30 mm away from the
right edge of the electrode 83 toward the right side, to a position
that is approximately 30 mm away from the left edge of the
electrode 83 toward the left side, such that the slits 97 are
formed to have a length of 60 mm as viewed from the direction in
which the electrode 83 extends. The area outside the area where the
slits 97 are formed, i.e., on the center side of the area where the
electrode 83 is wound around, openings 98 are formed in the Faraday
shield 95 at the rotational center side and the outer peripheral
side of the turntable 2. Note that in FIG. 3, the slits 97 are not
illustrated. Furthermore, in FIGS. 4 and 5, the slits 97 are
illustrated in a simplified manner, but, for example, actually
about 150 slits 97 are formed. The slits 97 are actually formed
such that the width d1 increases from the area in close contact
with the opening 98 toward the area that is away from the opening
98, but, such a configuration of the slits 97 is not illustrated in
the drawings.
[0070] Although only the first plasma generation unit 80 has been
described in detail, the second plasma generation unit 130 and the
case 140 can be configured as well as the first plasma generation
unit 80 and the case 90. Hence, a description of the second plasma
generation unit 130 is omitted.
[0071] Next, the description of the elements of the processing
chamber 1 is continued. At a position that is slightly lower than
the turntable 2 on the outer peripheral side of the turntable 2, as
illustrated in FIGS. 2, 5, and 10, a side ring 100 that is a cover
body is arranged. For example, the side ring 100 is used for
protecting the inner walls of the processing chamber 1 from a
cleaning gas, when the apparatus is cleaned and a
fluoride-containing cleaning gas is circulated through the
apparatus instead of processing gases. That is to say, unless the
side ring 100 is provided, a recessed airflow passage in which an
airflow (exhaust flow) is formed in the horizontal direction is
formed in a ring shape along the circumferential direction between
the outer peripheral part of the turntable 2 and the inner walls of
the processing chamber 1. Therefore, the side ring 100 is provided
in the airflow passage, such that the inner walls of the processing
chamber 1 are exposed to the airflow passage as little as possible.
In this example, the separation area D and the area on the outer
edge side of the case 90 are exposed to the upper side of this side
ring 100.
[0072] On the top surface of the side ring 100, exhaust openings
61, 62 are formed at two locations that are spaced apart from each
other in the circumferential direction. In other words, two exhaust
ports are formed on the lower side of the airflow passage, and the
exhaust openings 61 and 62 are formed in the side ring 100 at
positions corresponding to the exhaust ports of the airflow
passage. Among these two exhaust openings 61 and 62, one is
referred to as a first exhaust opening 61 and the other one is
referred to as a second exhaust opening 62. The first exhaust
opening 61 is formed at a position shifted toward the separation
area D relative to the first plasma gas nozzle 31 between the first
plasma gas nozzle 31 and the separation area D at the downstream
side in the rotational direction of the turntable 2. The second
exhaust opening 62 is formed at a position shifted toward the
separation area D relative to the second plasma gas nozzle 32
between the second plasma gas nozzle 32 and the separation area D
at the downstream side in the rotational direction of the turntable
2. The first exhaust opening 61 is for exhausting the first plasma
gas for etching and the separation gas, and the second exhaust
opening 62 is for exhausting the second plasma gas for modification
and the separation gas. As illustrated in FIG. 1, the first exhaust
opening 61 and the second exhaust opening 62 are connected to, for
example, a vacuum pump 64, which is a vacuum exhaust mechanism, by
an exhaust pipe 63 provided with a pressure adjustment unit 65 such
as a butterfly valve.
[0073] Here, as described above, the cases 90 and 140 are provided
from the central area C to the outer edge side of the turntable 2.
Therefore, when various kinds of gases, which are discharged to the
upstream side in the rotational direction of the turntable 2 with
respect to the cases 90 and 140, the gas flows going toward the
second exhaust openings 61 and 62 are regulated by the cases 90 and
140, respectively. Thus, gas flow paths 101 and 102 shaped as gaps
through which the first and second plasma gas and the separation
gas flow therethrough are formed in the top surface of the side
ring 100 at the outside of the cases 90 and 140, respectively.
Specifically, as illustrated in FIG. 3, the gas flow paths 101 and
102 are formed into an arc shape extending from a position closer
to the first and second plasma gas nozzles 31 and 32 by, for
example, approximately 60 mm, than the edge of the upstream side in
the rotational direction of the turntable 2 of the cases 90 and
140, to the first and second exhaust openings 61 and 62,
respectively, so as to have the depth of, for example, 30 mm.
Accordingly, the gas flow paths 101 and 102 are formed so as to
extend along the outer edges of the cases 90 and 140, and to cross
the outer edge parts extending in the radial direction of the cases
90 and 140 as viewed from above. Although not illustrated, the
surface of this side ring 100 is coated by, for example, alumina,
or is covered by a quartz cover, for the purpose of applying a
corrosion resistance property with respect to fluorinated gas.
[0074] As illustrated in FIG. 2, in the center part of the bottom
surface of the ceiling plate 11, a protrusion part 5 is provided.
Specifically, the protrusion part 5 is formed in a substantially
ring shape along the circumferential direction in continuation with
the part on the central area C side of the convex portion 4, and
the bottom surface of the protrusion part 5 is formed to be at the
same height as the bottom surface of the convex portion 4 (ceiling
surface 44). Above the core part 21 closer to the rotational center
side of the turntable 2 than the protrusion part 5, the labyrinth
structure part 110 is arranged, which is for preventing the first
plasma gas and the second plasma gas from mixing with each other at
the central area C. That is to say, as illustrated in FIG. 1, the
case 90 is formed up to a position close to the central area C
side, and therefore in the core part 21 supporting the center part
of the turntable 2, the part above the turntable 2 is formed at a
position closer to the rotational center to avoid the case 90.
Accordingly, for example, the different types of processing gases
are more easily mixed with each other on the central area C side
than on the outer edge side. Thus, by forming the labyrinth
structure part 110, the gas flow path is extended and the different
types of processing gases are prevented from being mixed with each
other. In FIG. 1, although the case 140 is not illustrated, the
case 140 has a structure similar to the case 90.
[0075] As illustrated in FIG. 1, in the space between the turntable
2 and the bottom part 14 of the processing chamber 1, a heater unit
7 that is a heating mechanism is provided. For example, the heater
unit 7 heats the wafer W on the turntable 2 up to 300.degree. C.,
through the turntable 2. FIG. 1 illustrates a cover member 71a
provided on the side of the heater unit 7, and a hood member 7a
covering the upper side of the heater unit 7. Furthermore, purge
gas supply pipes 73 for purging the space where the heater unit 7
is arranged, are provided in the bottom part 14 of the processing
chamber 1 below the heater unit 7 at a plurality of positions along
the circumferential direction.
[0076] As illustrated in FIGS. 2 and 3, the transfer opening 15 is
formed in the side wall of the processing chamber 1 for
transferring wafers W, between an external transfer arm (not
illustrated) and the turntable 2. This transfer opening 15 can be
opened and closed in a gastight manner by a gate valve G.
Furthermore, because wafers W are transferred between the transfer
arm and the recessed portions 24 of the turntable 2 at the position
facing the transfer opening 15, lift pins for lifting the wafer W
from below through the recessed portions 24 and a lifting mechanism
for the lift pins are provided (neither are illustrated) below the
turntable 2 at the part corresponding to the position where the
wafers W are transferred.
[0077] Moreover, as illustrated in FIG. 1, the etching apparatus is
provided with a control unit 120 constituted by a computer for
controlling the operations of the entire apparatus. The control
unit 120 includes a CPU (Central Processing Unit) 121 and a memory
122. The memory 122 of the control unit 120 stores programs for
performing an etching process and a modifying process described
below. The CPU 121 reads these programs and executes the programs.
These programs include a group of steps for executing operations of
the apparatus described below, and the programs are installed in
the memory 122 in the control unit 120 from a storage unit 125 that
is a storage medium such as a hard disk, a compact disk, a magnetic
optical disk, a memory card, and a flexible disk.
[0078] The control unit 120 controls the entire process control
including a plasma process control according to a process recipe.
Specific control and process contents of the plasma process control
may be provided in a form of a conditioning recipe as well as the
process recipe. For example, the process recipe and the
conditioning recipe are installed from the storage unit 125 to the
memory 122 in the control unit 120, and may be executed by the CPU
121.
[0079] Next, a description is given below of a plasma processing
method according to an embodiment of the present invention. The
plasma processing method of the present invention can be applied to
a plasma processing apparatus other than the above-mentioned plasma
processing apparatus as long as the plasma processing apparatus can
periodically switch between an etching process and a modification
process in a relatively short period of time. However, because the
above-mentioned plasma processing apparatus can preferably perform
the plasma processing method of the present invention, a
description is given below of the plasma processing method
according to the embodiment of the present invention by citing an
example of using the above-mentioned plasma processing apparatus.
Moreover, in the plasma processing method according to the
embodiment of the present invention, a description is given below
of an example of applying the plasma processing method of the
present invention to an etching processing method.
[0080] FIGS. 11A through 11D are a series of process drawings
illustrating an example of the plasma processing method according
to an embodiment of the present invention. FIG. 11A is a diagram
illustrating an example of a plasma processing substrate
preparation process. In the plasma processing substrate preparation
process, a wafer W on which a film 160 to be etched is deposited is
prepared. As illustrated in FIG. 11A, a recessed pattern 150 may be
formed in a surface of the wafer W. The recessed pattern 150 is a
wiring pattern including a recessed shape formed in the surface of
the wafer W, and includes a groove shaped trench, a well-shaped
hole having a high aspect ratio and the like. In the embodiment, a
description is given below of an example of the film 160 being a
SiO.sub.2 film.
[0081] More specifically, to begin with, the gate valve G is opened
(see FIGS. 2 and 3), and for example, five wafers W are placed on
the turntable 2 by a transfer arm (not illustrated in the drawings)
through the transfer opening 15 while rotating the turntable 2
intermittently. Next, the gate valve G is closed, and the
processing chamber 1 is continued to be evacuated by the vacuum
pump 64, and then the wafers W are heated by the heater unit 7 up
to, for example, about 250 through 600.degree. C. while rotating
the turntable 2 in a clockwise fashion. Although the temperature of
the wafers W is set at a variety of temperatures depending on the
intended use, the temperature of the wafers W may be set at about
400.degree. C. Also, although a pressure in the processing chamber
1 may be set at a variety of pressure values depending on the
intended use, for example, the pressure may be set at 2 Torr.
[0082] Although the rotational speed of the turntable 2 varies
depending on a process, for example, the rotational speed of the
turntable 2 may be set in a rage of 1 to 240 rpm, or preferably in
a range of 20 to 240 rpm.
[0083] Subsequently, the first plasma gas nozzle 31 supplies a
mixed gas of Ar gas and NF.sub.3 gas to the first plasma processing
area P1, and the second plasma gas nozzle 32 supplies a mixed gas
of Ar gas and H.sub.2 gas to the second plasma processing area P2.
Moreover, the separation gas nozzles 41 and 42 supplies Ar gas at a
predetermined flow rate as a separation gas (or a purge gas), and
the separation gas supply pipe 51 and the purge gas supply pipes 72
and 73 supply Ar gas at a predetermined flow rate. Then, the inside
of the processing chamber 1 is adjusted to a preset processing
pressure by the pressure adjustment unit 65. Furthermore, high
frequency power is supplied to the first and second plasma
generation units 80 and 130.
[0084] The flow rate of each of the gases may be set at a variety
of flow rates depending on the intended use. For example, as a
guide, a flow rate of Ar gas from the separation gas supply pipe 51
may be set at about 1 slm; a flow rate of Ar gas from the
separation gas nozzles 41 and 42 may be set at about 5 slm; a flow
rate of Ar gas from the first plasma gas nozzle 31 is set at 10
slm; flow rates of Ar gas and NF.sub.3 gas from the second plasma
gas nozzle 32 are set at about 10 slm and 0.1 slm, respectively;
and flow rates of Ar gas and H.sub.2 gas from the second plasma gas
nozzle 32 may be set at about 10 slm and 2 slm, respectively.
[0085] FIG. 11B is a diagram illustrating an example of an etching
process. The etching process is performed by rotating the turntable
2 and at the time the wafer W passes through the first plasma
processing area P1. When the wafer W passes through the first
plasma processing area P1, the film 160 is etched by plasma of Ar
and F. Ar gas and NF.sub.3 gas supplied from the first plasma gas
nozzle 31 is converted into plasma by the first plasma generation
unit 80, and the plasma etches the SiO.sub.2 film 160. Even if the
turntable 2 rotates at a relatively slow rotational speed, for
example, of 20 rpm, because the turntable 2 requires just three
seconds to rotate one revolution, the wafer W passes through the
first plasma processing area P1 in a period shorter than 3 seconds.
Hence, the etching process is performed on the film 160 in a short
time that is shorter than three seconds. More exactly, because the
first plasma processing area P1 has an area at most one fourth of
the entire area of the turntable 2, the etching process is
performed in a short time that is shorter than 0.75 seconds. In the
etching process, because a fluoride component remains in the film
160, a state of the film 160 differs from a state illustrated in
FIG. 11A, and the state illustrated in FIG. 11B is made a film
161.
[0086] FIG. 11C is a diagram illustrating an example of a
modification process. The modification process is performed by
rotating the turntable 2 and at the time the wafer W passes through
the second plasma processing area P2 after passing through the
separation area D. The wafer W is purged and cleaned by Ar gas that
is the separation gas supplied from the separation gas nozzle 41
when passing through the separation area D. Then, after passing
through the separation area D and when the wafer W passes through
the second plasma processing area P2, the film 161 is modified by
plasma of Ar and H. Ar gas and H.sub.2 gas supplied from the second
plasma gas nozzle 32 is converted into plasma by the second plasma
generation unit 130, and the plasma reacts with the fluoride
component in the SiO.sub.2 film and releases from the SiO.sub.2
film by becoming HF, thereby reducing the F component in the
SiO.sub.2 film 161. The reaction on this occasion is expressed in
the following chemical formula (2).
H+HF.fwdarw.HF (2)
[0087] As described in FIG. 11B, even if the turntable 2 rotates at
a relatively slow rotational speed of, for example, 20 rpm, because
one revolution is finished in three seconds, the wafer W passes
through the second plasma processing area P2 in a period shorter
than three seconds. Hence, the modification process for less than
three seconds is performed on the film 160. More exactly, because
the second processing area P2 has an area at most one fourth of the
entire area of the turntable 2, the modification process is
performed in a short time of less than 0.75 seconds. Here, because
the fluoride component disappears or decreases in the film 161 in
the modification process, the quality of film 161 returns to a
state similar to the state illustrated in FIG. 11A. This state of
the film in which the film quality has been recovered is
hereinafter expressed as the film 160 that is the same as the film
160 in FIG. 11A.
[0088] The wafer W passes the separation area D located on the
downstream side of the second plasma processing area P2 in the
rotational direction of the turntable 2 after passing the second
plasma processing area P2, and is purged and cleaned by receiving
the supply of Ar gas from the separation gas nozzle 42. Then, the
wafer W has passed the separation area D.
[0089] Here, because the turntable 2 continuously keeps rotating,
the etching process illustrated in FIG. 11B and the modification
process illustrated in FIG. 11C are repeated in the same period
until the turntable 2 stops. The cycle becomes three seconds even
when the rotational speed is 20 rpm that is relatively slow. When
the rotational speed is 240 rpm that is fast, the cycle is 0.25
seconds. The cycle is, for example, in a range of 0 to 60 seconds,
preferably in a range of 0 to 30 seconds, further preferably in a
range of 0.25 to 3 seconds. Hence, by rotating the turntable 2, a
cycle constituted of an etching process, a purge process, a
modification process and a purge process in a very short time, are
repeated a plurality of times in the same period. Naturally, the
quantity of etching and the quantity of modification become an
atomic layer level, and an etching process by ALE (atomic layer
etching) and a modification process after the etching is performed
alternately and periodically. Repeating such a very small quantity
of etching process and a very small quantity of modification
process is very effective to form a high-quality etching film
having a low fluoride content. In general, in a conventional
etching process, different from the etching process according to
the embodiment, the etching process illustrated in FIG. 11B has
been continuously performed for a certain amount of long time, and
the modification process illustrated in FIG. 11C has been
continuously performed for a certain amount of long time. However,
in this case, the fluoride component has not been often able to be
reduced sufficiently due to an insufficient modification process.
In the plasma processing method of the embodiment, the fluoride
component in the film 160 can be efficiently removed. In this
regard, a detailed description is given below with reference to
FIGS. 12A and 12B.
[0090] FIGS. 12A and 12B are diagrams for explaining the
modification process of the plasma processing method according to
the embodiment. FIG. 12A is a diagram for explaining an O.sub.2
plasma modification process performed during a film deposition of a
SiO.sub.2 film. As illustrated in FIG. 12A, when the SiO.sub.2 film
is deposited, in general, a modification process by an oxidation
gas such as O.sub.2 gas, O.sub.3 gas or the like. O.sub.2 gas is
converted into plasma, and O(.sup.3P) reaches the inside of the
SiO.sub.2 film and can oxidize a Si substrate. Moreover, although O
(.sup.1P) has a short life time and cannot reach a deep location in
the film, because the reactivity is very high, modifying a surface
of the SiO.sub.2 film is possible. In other words, during the film
deposition of the SiO.sub.2 film, by performing the O.sub.2 plasma
modification process for a certain amount of time after depositing
the SiO.sub.2 film up to a predetermined film thickness, the
modification process by oxidation can be performed to the inside of
the film.
[0091] FIG. 12B is a diagram for explaining an H.sub.2 plasma
modification process performed while etching the SiO.sub.2 film. As
illustrated in FIG. 12B, when etching the SiO.sub.2 film, in
general, the modification process by H.sub.2 gas is performed.
Although H.sub.2 plasma has a high reactivity, because the life
time is short, the H.sub.2 plasma does not reach a deep location
inside the film, and a modification reaction inevitably occurs at a
surface of the film. Due to this, even if the etching process is
performed for a long time until etching up to a predetermined
quantity of etching and then the modification process of the film
is tried to be performed on the etched film all at once, the H
plasma does not reach the inside of the film, which makes it
difficult to remove the fluoride component. Accordingly, the plasma
processing method of the embodiment of performing a small quantity
of modification process after performing a small quantity of
etching is very effective to remove the fluoride component from the
film, which makes it possible to efficiently remove or reduce the
fluoride component in the SiO.sub.2 film.
[0092] FIG. 13 is a graph showing analysis results of a fluoride
concentration in a SiO.sub.2 film after performing a conventional
modification process. In FIG. 13, a residual fluoride concentration
in a film without being subject to an etching process is expressed
by a curve N; a residual fluoride concentration in a film subject
to an etching process and a modification process is expressed by a
curve M; and a residual fluoride concentration in a film being only
subject to an etching process without an modification process is
expressed by a curve L under conditions in which a temperature is
the processing chamber 1 is 400.degree. C.; a rotational speed of
the turntable 2 is 60 rpm; an output of the high frequency power
source is 1500 W: a flow rate of Ar gas is 10 kcc; a flow rate of
an etching gas is 50 cc.
[0093] As illustrated in FIG. 13, the curves L and M subject to the
etching both have residual fluoride concentrations much higher than
the residual fluoride concentration of the curve N. The fluoride
concentration of the curve M subject to the modification process is
lower than the fluoride concentration of the curve L in an area
that is shallower than 3 nm from the surface, which is a shallow
area of the film, and the slight effect of reducing the fluoride
concentration can be found. However, the effect is small, and the
effect of reducing the fluoride concentration can be hardly found
in an area equal to or deeper than 5 nm of the film. In this
regard, the results agree with the contents described in FIGS. 12A
and 12B.
[0094] A description is given below with reference to FIGS. 11A
through 11D again. As described in FIGS. 11B and 11C, by repeating
the small quantity of etching process and the modification process
for removing the small quantity of fluoride at the surface, the
problem of the conventional technique described in FIGS. 12A, 12B
and 13 can be solved, and a SiO.sub.2 film containing a low
fluoride component can be formed.
[0095] FIG. 11D is a diagram illustrating an example of a filling
process. In the filling process, after finishing desired etching
process and modification process, filling a recessed pattern 150 is
performed as necessary. Because the etching process and the
modification process have finished in FIGS. 11B and 11C, the
process illustrated in FIG. 11D does not have to be performed when
the plasma processing method includes only the etching process. In
contrast, by repeating the film deposition illustrated in FIGS. 11A
through 11C and the etching process, the recessed pattern 150 may
be gradually filled. The plasma processing method of the embodiment
can be applied to a variety of processes including the etching
process.
[0096] After finishing the substrate process including the etching,
the wafer W is carried out of the processing chamber 1 in a reverse
manner to carrying the wafer W into the processing chamber 1, and a
predetermined substrate process finishes.
[0097] FIGS. 14A and 14B are diagrams showing simulation results
indicating an isolation state of hydrogen gas in the plasma
processing apparatus of the embodiment. FIG. 14A is a diagram
showing an isolation state of hydrogen gas when the rotational
speed of the turntable 2 is set at 20 rpm, and FIG. 14B is a
diagram showing an isolation state of hydrogen gas when the
rotational speed of the turntable 2 is set at 240 rpm.
[0098] As discussed above, NF.sub.3 gas of an etching gas and
H.sub.2 gas of a modification gas cause an explosion when being
mixed in a predetermined concentration range, and even if the
explosion is not caused, if HF is produced, HF adversely affects
the inner wall of the processing chamber 1. Hence, NF.sub.3 gas and
H.sub.2 gas are preferred to be completely isolated from each
other. Accordingly, in order to understand an isolation status of a
modification gas and an etching gas while the plasma processing
apparatus of the embodiment performs the plasma processing method
of the embodiment, simulation experiments was performed.
[0099] FIGS. 14A and 14B illustrate mass concentrations of H.sub.2
gas of a modification gas. The simulation conditions is as follows:
a pressure in the processing chamber 1 is 2 Torr; a temperature of
a wafer W is 400.degree. C.; a flow rate of Ar gas from the
separation gas supply pipe 51 is 1 slm; a flow rate of Ar gas from
the separation gas nozzles 41 and 42 is 5 slm; flow rates of Ar gas
and NF.sub.3 gas from the first plasma gas nozzle 31 are 10 slm and
0.1 slm, respectively; and flow rates of Ar gas and H.sub.2 gas
from the second plasma gas nozzle 32 are 10 slm and 2 slm,
respectively.
[0100] As illustrated in FIGS, 14A and 14B, in both cases of the
rotational speed of the turntable 2 being 20 rpm and 240 rpm, areas
Q and R where the mass ratio of hydrogen are high almost match the
second plasma processing area P2. Although areas S, T and O having
middle degrees of mass ratio of hydrogen and areas U and V having
low degrees of mass ratio of hydrogen slightly run out downstream
of the second plasma processing area P2 in the rotational direction
of the turntable 2 by being pulled by the rotation of the turntable
2, the other is an area W having a mass ratio of hydrogen of
approximately zero. Here, the area having high mass ratios of
hydrogen is larger in FIG. 14B of higher rotational speed of the
turntable 2 than in FIG. 14A of lower rotational speed of the
turntable 2, but the area V does not still reach the separation
area D. Accordingly, the results indicate that an isolation
capability of hydrogen gas in the second plasma processing area P2
and one in the separation area D are sufficiently high, and that
there is no problem about the isolation of hydrogen gas.
[0101] FIGS. 15A and 15B are diagrams showing simulation results
indicating an isolation state of NF.sub.3 gas in the plasma
processing apparatus of the embodiment. FIG. 15A is a diagram
showing an isolation state of NF.sub.3 gas when the rotational
speed of the turntable 2 is set at 20 rpm, and FIG. 15B is a
diagram showing an isolation state of NF.sub.3 gas when the
rotational speed of the turntable 2 is set at 240 rpm.
[0102] The simulation conditions are the same as the conditions
described in FIGS. 14A and 14B. In FIGS. 15A and 15B, areas Q and R
having high mass ratio of NF.sub.3 gas stay in the vicinity of the
first plasma processing area P1. Although areas S, T and O having
middle mass ratios of fluoride and areas U and V having low mass
ratio of fluoride slightly go beyond the first plasma processing
area P1 on both sides in the rotational direction of the turntable
2, fluoride is completely isolated by the separation area D located
downstream of the first plasma processing area P1 in the rotational
direction of the turntable 2, and the separation area D and an area
downstream of the separation area are in an area W having a mass
ratio of fluoride of approximately zero. On the upstream side, even
a location that does not reach the separation area D far therefrom
is in an area W having the mass ratio of fluoride of approximately
zero. Naturally, the mass ratio of fluoride is approximately zero
in an area including the second plasma processing area P2 and
sandwiched between the separation areas D (area W). Accordingly,
the results indicate that an isolation capability of NF.sub.3 gas
of the first plasma processing area P1 and an isolation capability
of NF.sub.3 gas of the separation areas D are sufficiently high,
and that there is no problem about the isolation of NF.sub.3
gas.
[0103] FIGS. 16A and 16B are diagrams showing simulation results
indicating an isolation state of a separation gas in the plasma
processing apparatus of the embodiment in terms of a pressure. FIG.
16A is a diagram showing a pressure state in the processing chamber
1 when the rotational speed of the turntable 2 is set at 20 rpm,
and FIG. 15B is a diagram showing a pressure state in the
processing chamber 1 when the rotational speed of the turntable 2
is set at 240 rpm.
[0104] The simulation conditions are the same as the conditions
described in FIGS. 14A and 14B. Hence, the pressure in the
processing chamber 1 is set at 2 Torr. As illustrated in FIGS. 16A
and 16B, although the pressure of the separation gas nozzles 41 and
42 and the surroundings thereof are included in areas Q, R, S and T
having high pressures, the other area is included in areas U and V
having a middle pressure and a slightly low pressure, respectively.
This indicates that the pressures of the separation gas nozzles 41
and 42 and the surroundings thereof are higher than the other area
and that there is no problem about a gas isolation capability of
the separation areas D. Therefore, the results indicated that the
separation areas D do not have any problem about the gas isolation
capability in terms of the pressure.
[0105] FIGS. 17A and 17B are diagrams showing simulation results
indicating an isolation state of a separation gas in the plasma
processing apparatus of the embodiment in terms of amass
concentration of Ar. FIG. 17A is a diagram showing a mass
concentration of Ar in the processing chamber 1 when the rotational
speed of the turntable 2 is set at 20 rpm, and FIG. 17B is a
diagram showing a mass concentration of Ar in the processing
chamber 1 when the rotational speed of the turntable 2 is set at
240 rpm.
[0106] As illustrated in FIGS. 17A and 17B, while an area Q having
a high mass concentration of Ar dominates areas other than the
separation areas D and the first and second plasma processing areas
P1 and P2, an area V having a low mass concentration of Ar
dominates the areas in the first and second plasma processing areas
P1 and P2. This indicates that there is no problem about a gas
isolation capability by Ar gas supplied from the separation gas
areas D as a purge gas. In other words, the gas concentration of Ar
gas differs in area, which shows the high gas isolation capability.
Accordingly, the results indicate that the separation areas D do
not have any problem about the gas isolation capability in terms of
the mass concentration of Ar.
[0107] In this manner, the plasma processing apparatus of the
embodiments has a high gas isolation capability. Thus, H.sub.2 gas
and NF.sub.3 gas that can cause a problem when being mixed with
each other can be supplied into the processing chamber 1 at the
same time, and a fluoride component in a film can be efficiently
removed or reduced by periodically performing ALE and a small
quantity of modification process. This allows a film to be etched
while keeping a film quality high.
[0108] Although the plasma processing apparatus and the plasma
processing method according to the embodiments have been described
by citing an example of performing an etching process on a
SiO.sub.2 film, the etching process can be performed on a variety
of films including a SiN film and a TiN film.
[0109] Moreover, in addition to the etching process, as long as a
process needs two different types of plasma processes, the plasma
processing apparatus and the plasma processing method of the
embodiment can be preferably applied to the process. For example,
the plasma processing apparatus and the plasma processing method of
the embodiment can be applied to a variety of processes such as a
film deposition process, a process of filling a recessed pattern
with a film by performing both of a film deposition process and an
etching process alternately and the like.
[0110] According to the embodiments of the present invention, an
etching can be performed while reducing a fluoride concentration in
a film.
[0111] All examples and conditional language recited herein are
intended for pedagogical purposes to aid the reader in
understanding the embodiments and the concepts contributed by the
inventor to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions, nor does the organization of such examples in the
specification relate to a showing of superiority or inferiority of
the embodiments. Although the method of manufacturing the silicon
oxide film has been described in detail, it should be understood
that the various changes, substitutions, and alterations could be
made hereto without departing from the spirit and scope of the
invention.
* * * * *